Method of making flash memory cells and peripheral circuits having sti, and flash memory devices and computer systems having the same

ABSTRACT

An integrated circuit includes flash memory cells, and peripheral circuitry including low voltage transistors (LVT) and high voltage transistors (HVT). The integrated circuit includes a tunnel barrier layer comprising SiON, SiN or other high-k material. The tunnel barrier layer may comprise a part of the gate dielectric of the HVTs. The tunnel barrier layer may constitute the entire gate dielectric of the HVTs. The corresponding tunnel barrier layer may be formed between or upon shallow trench isolation (STIs). Therefore, the manufacturing efficiency of a driver chip IC may be increased.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a Divisional of U.S. application Ser. No. 12/367,988filed on Feb. 9, 2009, which claims priority to Korean PatentApplication No. 10-2008-59077, filed on Jun. 23, 2008, in the KoreanIntellectual Property Office (KIPO), the disclosures of which areincorporated by reference herein in their entireties.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention generally relates to flash memory devices, andmore particularly, to a method of forming flash memory cells andperipheral circuitry of flash memory devices having shallow trenchisolation (STI) and flash memory devices produced thereby.

2. Discussion of the Related Art

Non-volatile memory devices, such as flash memory devices, may beprovided in a NOR-type configuration or a NAND-type configuration.NAND-type nonvolatile semiconductor memory devices have a plurality ofelectrically rewritable nonvolatile memory cells connected in seriestogether.

Two types of non-volatile memory cells are floating gate type memorycells and floating trap (charge trap) type memory cells. A floating gatetype memory device may include a control gate and a conductive floatinggate that is isolated, by an insulating layer, from a field effecttransistor (FET) channel formed in a substrate. Floating gate typememory devices may be programmed by storing charges as free carriers onthe conductive floating gate.

The multi-tunnel barrier of charge trap type is described in US PatentNos. 20060198190, 20060202262, 20060202252, the disclosures of which arecollectively, incorporated by reference herein. The multi-tunnel barrierof floating gate type is described in U.S. Pat. Nos. 6,784,484 and7,026,686, the disclosures of which are collectively incorporated byreference herein.

Floating trap (charge trap) type memory devices may include anon-conductive charge storage layer between a gate electrode and a fieldeffect transistor (FET) channel formed in a substrate. Floating traptype memory devices may be programmed by storing charges in traps in thenon-conductive charge storage layer.

A floating gate type memory cell is similar to a standard MOSFETtransistor, except that it has two gates instead of just one. One gateis the control gate (CG) like in other MOSFET transistors, but thesecond gate is a floating gate (FG) that is insulated all around by anoxide insulator. The floating gate (FG) is between the control gate (CG)and the substrate. Because the FG is isolated by its insulating oxidelayer, any electrons placed on it get trapped there and thus store theinformation.

When electrons are trapped on the FG, they modify (partially cancel out)an electric field coming from the CG, which modifies the thresholdvoltage (Vt) of the cell. Thus, when the cell is “read” by placing aspecific voltage on the control gate (CG), electrical current willeither flow or not flow between the cell's source and drain connections,depending on the threshold voltage (Vt) of the cell. This presence orabsence of current is sensed and translated into 1's and 0's,reproducing the stored data.

A conventional floating trap type unit memory device may include a SONOS(silicon-oxide-nitride-oxide-semiconductor) structure (layers). One verybasic type of SONOS device may include a polycrystalline silicon(“polysilicon”, poly-Si) gate formed over a dielectric layer thatincludes a silicon nitride layer sandwiched between silicon oxidelayers.

A floating trap type non-volatile memory device uses trap levels, suchas those found in a silicon nitride layer, for memory operations. When apositive voltage is applied on the gate electrode, electrons aretunneled via the tunneling insulating layer to become trapped in thecharge storage layer. As the electrons are accumulated in the chargestorage layer, a threshold voltage of the memory device is increased,and the memory device becomes programmed. In contrast, when a negativevoltage is applied to the gate electrode, trapped electrons aredischarged to the semiconductor substrate via the tunneling insulatinglayer. Concurrently, holes become trapped by the tunneling insulatinglayer. Consequently, the threshold voltage of the unit memory device isdecreased, and the memory device becomes erased.

Flash memory devices may have three types of transistors which are: thememory cell transistors (implementing nonvolatile data-storage memorycells); low voltage transistors; and high voltage transistors. Shallowtrench isolation (STI), also known as ‘Box Isolation Technique’, is anintegrated circuit feature that prevents electrical current leakagebetween adjacent semiconductor device components. STI is generally usedon CMOS process technology nodes of 250 nanometers and smaller. STI istypically created early during the semiconductor device fabricationprocess, before transistors are formed. The key steps of the STI processinvolve etching a pattern of trenches in the silicon substrate,depositing one or more dielectric materials (such as silicon dioxide) tofill the trenches, and removing the excess dielectric material using atechnique such as chemical-mechanical planarization (CMP).

SUMMARY OF THE INVENTION

Floating trap type non-volatile memory devices according to someembodiments of the present invention include a semiconductor substrateand memory cell transistors having gate electrodes. Between thesubstrate and the gate electrode may be a tunneling insulating layerhaving a first dielectric constant, a charge storage layer, and ablocking insulating layer. Floating trap type non-volatile memorydevices according to some embodiments of the present invention include asemiconductor substrate with a plurality of parallel active regions. Aplurality of memory cell transistor gate electrodes are formed over theactive regions.

An aspect of the present invention provides an integrated circuit,comprising: a memory cell region having a plurality of memory celltransistors, each memory cell transistor including a tunnel barrierlayer formed on a substrate, and a charge storage layer formed above thetunnel barrier layer and a blocking layer formed above the chargestorage layer, and its transistor gate electrode formed above theblocking layer; a first trench isolation (TI) formed in the memory cellregion for isolating at least one of the memory cell transistors; aperipheral region outside of the memory cell region including lowvoltage transistors and high voltage transistors, wherein each of thelow voltage transistors (LVT) and the high voltage transistors (HVT)includes the tunnel barrier layer; a second trench isolation (TI) formedin the peripheral region for isolating at least one of the low voltagetransistors; and a third trench isolation (TI) formed in the peripheralregion for isolating at least one of the high voltage transistors,wherein the tunnel barrier layer includes a first dielectric layer and asecond dielectric layer.

In preferred embodiments, each of the memory cell transistors, the lowvoltage transistors and the high voltage transistors is a field effecttransistor (FET) having a transistor gate.

The tunnel barrier layer may be formed over the first trench isolationin the memory cell region. The tunnel barrier layer may be formed uponthe second trench isolation TI and upon the third trench isolation TI inthe peripheral region. The first trench isolation TI in the memory cellregion may include oxide, and the tunnel barrier layer is formed uponthe first trench isolation TI in the memory cell region. The tunnelbarrier layer may be continuously formed in the plurality of memory celltransistors and upon the first trench isolation TI in the memory cellregion. The first dielectric layer of the tunnel barrier layer may havea higher K than the second dielectric layer of the tunnel barrier layer.The first dielectric layer of the tunnel barrier layer may compriseSiON, SiN, Al2O3, HfO2, HfSiON, or ZrO2. At least one of the firsttrench isolation (TI), the second trench isolation (TI) and the thirdtrench isolation (TI) may comprise the same dielectric material as thesecond dielectric layer of the tunnel barrier layer. The gate dielectricof the HVT may comprises the tunnel barrier layer plus an oxide layerthicker than the tunnel barrier layer.

The third trench isolation TI in the peripheral region may includeoxide, and the tunnel barrier layer may be formed upon the third trenchisolation TI in the peripheral region.

In alternative embodiments, the tunnel barrier layer is not formed uponthe second trench isolation TI and is not formed upon the third trenchisolation TI in the peripheral region. And, the tunnel barrier layer maynot be formed upon the first trench isolation TI in the memory cellregion.

In some embodiments, the tunnel barrier layer formed within the memorycell region further includes a third dielectric layer of the tunnelbarrier layer, wherein the first dielectric layer of the tunnel barrierlayer is formed over the third dielectric layer of the tunnel barrierlayer, and the second dielectric layer of the tunnel barrier layer isformed over the first dielectric layer of the tunnel barrier layer.

In some embodiments, the charge storage layer comprises floating gatesof the memory cell transistors.

First and second memory cell transistors may be formed in a NAND typestring, wherein the first trench isolation (TI) formed in the memorycell region isolates the string comprising the first and second memorycell transistors. The storage layer and blocking layer of the firstmemory cell transistor in the string may be patterned disconnected fromthe storage layer and the blocking layer of a second memory celltransistor in the string.

Another aspect of the invention provides an integrated circuit,comprising: a memory cell region having a plurality of memory celltransistors, each memory cell transistor including a tunnel barrierlayer formed on a substrate, and a charge storage layer formed above thetunnel barrier layer and a blocking layer formed above the chargestorage layer, and its transistor gate electrode formed above theblocking layer; a first trench isolation (TI) formed in the memory cellregion for isolating at least one of the memory cell transistors,wherein the tunnel barrier layer is formed in each of the plurality ofmemory cell transistors and upon the first trench isolation TI in thememory cell region.

The integrated circuit may further comprise: a peripheral region outsideof the memory cell region including low voltage transistors (LVT) andhigh voltage transistors (HVT); a second trench isolation (TI) formed inthe peripheral region for isolating at least one of the low voltagetransistors; a third trench isolation (TI) formed in the peripheralregion for isolating at least one of the high voltage transistors.

The tunnel barrier layer may includes a first dielectric layer and asecond dielectric layer, wherein the first dielectric layer of thetunnel barrier layer has a higher K than the second dielectric layer ofthe tunnel barrier layer. The first dielectric layer of the tunnelbarrier layer may comprise SiON, SiN, Al2O3, HfO2, HfSiON, or ZrO2.

The first and second memory cell transistors among the memory celltransistors may be formed in a NAND type string, wherein the firsttrench isolation (TI) formed in the memory cell region isolates thestring comprising the first and second memory cell transistors.

The gate dielectric of the low voltage transistors (LVT) may consistsessentially of the tunnel barrier layer. The gate dielectric of the highvoltage transistors (HVT) may comprise the tunnel barrier layer and anoxide layer. The tunnel barrier layer may be formed upon the secondtrench isolation (TI) formed and upon the third trench isolation (TI).

In alternative embodiments, none of the low voltage transistors (LVT)and the high voltage transistors (HVT) includes the tunnel barrierlayer.

The gate oxide layer of the HVT may be thicker than the gate oxide layerof the LVT.

Another aspect of the invention provides a method of forming anintegrated circuit on a substrate, the integrated circuit having amemory cell region including a plurality of memory cell transistors eachhaving a gate electrode, and a peripheral region including low voltagetransistors (LVT) and high voltage transistors (HVT) outside of thememory cell region. The method comprises: forming a first trenchisolation (TI) within the memory cell region for isolating at least oneof the memory cell transistors, and forming a second trench isolation(TI) for isolating at least one of the low voltage transistors (LVT) andforming a third trench isolation (TI) for isolating at least one of thehigh voltage transistors (HVT); and forming a tunnel barrier layerhaving first and second dielectric layers within the memory cell regionbetween the gate electrodes of the memory cell transistors and thesubstrate, and within the peripheral region.

Forming the tunnel barrier layer within the peripheral region mayinclude forming the tunnel barrier layer within the low voltagetransistors (LVT) and within the high voltage transistors (HVT). Thestep of forming the tunnel barrier layer may comprises the substeps of:forming the first dielectric layer; forming the second dielectric layerupon the first dielectric layer; and forming a third dielectric layerupon the a second dielectric layer, wherein the first dielectric layeris an oxide layer, the second dielectric layer is a nitride layer, andthe third dielectric layer is an oxide layer.

In some embodiments, the first, second, and third trench isolations maybe formed prior to forming the tunnel barrier layer, and the tunnelbarrier layer is formed upon the first trench isolation. In some suchembodiments, the tunnel barrier layer is formed upon the second trenchisolation and upon the third trench isolation.

In other embodiments, the first trench isolation, the second trenchisolation, and the third trench isolation may be formed after formingthe tunnel barrier layer, and the tunnel barrier layer is not formedupon the first trench isolation, nor upon the second trench isolationnor upon the third trench isolation.

In some embodiments of the invention, the step of forming the firsttrench isolation, the second trench isolation and the third trenchisolation may include the substeps of: forming a buffer layer (109) uponthe tunnel barrier layer; forming a stopper layer upon the buffer layer;etching the buffer layer, the stopper layer, and the substrate to formthe trenches; filling the trenches; and removing the buffer layer andstopper layer.

A method according to this aspect of the invention may further includethe steps of: forming a first conductive layer upon the tunnel barrierlayer; forming a blocking insulating layer upon the first conductivelayer; patterning the blocking insulating layer within the peripheralregion to form butting contact holes; patterning the blocking insulatinglayer within the memory cell region to form gate dielectrics of thememory cell transistors and butting contacts holes; forming a secondconductive layer upon the patterned blocking insulating layer andforming butting contacts connecting the first conductive layer and thesecond conductive layer within the gate electrodes of the LVT and HVT inthe peripheral region; and patterning the second conductive layer, theblocking insulating layer, and the first conductive layer within theperipheral region.

Another aspect of the invention provides a method of forming anintegrated circuit on a substrate, the integrated circuit having amemory cell region including a plurality of memory cell transistors eachhaving a gate electrode, and a peripheral region including low voltagetransistors (LVT) and high voltage transistors (HVT), outside of thememory cell region. The method comprises: forming the gate oxide layerupon the substrate within the peripheral region; forming a first trenchisolation (TI) within the memory cell region for isolating at least oneof the memory cell transistors, and forming a second trench isolation(TI) for isolating at least one of the low voltage transistors (LVT) andforming a third trench isolation (TI) for isolating at least one of thehigh voltage transistors (HVT); and forming a tunnel barrier layerhaving first and second dielectric layers within the memory cell regionbetween the gate electrodes of the memory cell transistors and thesubstrate, and upon the first trench isolation (TI) in the memory cellregion, wherein the gate oxide layer is thicker than the tunnel barrierlayer.

The step of forming the tunnel barrier layer may comprises the substepsof: forming the first dielectric layer; forming the second dielectriclayer upon the first dielectric layer; and forming a third dielectriclayer upon the a second dielectric layer, wherein the first dielectriclayer is an oxide layer, the second dielectric layer is a nitride layer,and the third dielectric layer is an oxide layer.

The method may further comprise the steps of: forming a charge storagelayer of the memory cell transistors upon the tunnel barrier layer ofthe within the memory cell region; forming blocking insulating layer ofthe memory cell transistors within the memory cell region, wherein theblocking insulating layer comprises SiO2, SiN, SiON, HfO2, ZrO, orAl2O3; forming a gate electrode conductive layer upon the blockinginsulating layer of the memory cell transistors within the memory cellregion; and patterning the blocking insulating layer, the charge storagelayer and the gate electrode conductive layer of the memory celltransistors within the memory cell region.

The method may comprise the additional steps of: patterning the blockinginsulating layer, the charge storage layer and the gate electrodeconductive layer of the memory cell transistors within the memory cellregion; forming inner spacers upon the vertical sides of the patternedblocking insulating layer, the charge storage layer and the gateelectrode conductive layer of the memory cell transistors within thememory cell region; patterning the blocking insulating layer and thecharge storage layer using the inner spacers as a mask; forming outerspacers upon the inner spacers; and doping the substrate using the outerspacers as a mask.

Another aspect of the invention provides a solid state memory module fora computer system, the module comprising: a housing; an interfaceconnector on the housing; a flash memory controller located within thehousing; the integrated circuits described above located within thehousing and electrically connected to the interface connector, theplurality of memory cell transistors in the integrated circuit beingarranged in an array for data storage and controlled by the flash memorycontroller. The solid state memory module may have an interfaceconnector being an IDE interface connector including a forty IDE pininterface and a power connector. The solid state memory module may be anSD card. The solid state memory module may alternatively have the formfactor of a MS (memory stick), CF (compact flash), SMC (smart media), orXD (XD-Picture Card), a hard disk drive, a cardbus card etc.

Another aspect of the invention provides a computer system comprisingthe solid state memory module described above. The computer system maybe a personal computer (PC), a personal digital assistant (PDA), an MP3player, a digital audio recorder, a pen-shaped computer, a digitalcamera, or a video recorder, etc.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other features of the present invention will becomereadily apparent by reference to the following detailed description whenconsidered in conjunction with the accompanying drawings wherein:

FIG. 1 is a block diagram of a computer system including a removablememory card including a flash memory device according to an embodimentof the present invention;

FIG. 2 f is a side cross-sectional view of three portions of anintegrated circuit containing a memory device according to an embodimentof the present invention;

FIGS. 2 a through 2 e are cross-sectional views depicting the steps of amethod of fabricating the memory device of FIG. 2 f;

FIG. 3 f is a side cross-sectional view of three portions of anintegrated circuit containing a memory device according to anotherembodiment of the present invention;

FIGS. 3 a through 3 e are cross-sectional views depicting the steps of amethod of fabricating the memory device of FIG. 3 f;

FIG. 4 is a side cross-sectional view of three portions of an integratedcircuit containing a memory device according to another embodiment ofthe present invention;

FIG. 5 h is a side cross-sectional view of three portions of anintegrated circuit containing a memory device;

FIGS. 5 a through 5 g are cross-sectional views depicting the steps of amethod of fabricating the memory device of FIG. 5 h; and

FIG. 6 is a block diagram of a computer system including a flash memorydrive according to an exemplary embodiment of the present invention.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS OF THE INVENTION

The present invention is described more fully hereinafter with referenceto the accompanying drawings, in which exemplary embodiments of thepresent invention are shown. The present invention may, however, beembodied in many different forms and should not be construed as limitedto the embodiments set forth herein. Rather, these embodiments areprovided so that this disclosure will be thorough and complete, and willfully convey the scope of the present invention to those skilled in theart. In the drawings, the sizes and relative sizes of layers and regionsmay be exaggerated for clarity of illustration.

It will be understood that when an element or layer is referred to asbeing “on,” “upon”, “connected to” or “coupled to” another element orlayer, it can be directly on, upon, connected or coupled to the otherelement or layer, or intervening elements or layers may be present. Incontrast, when an element is referred to as being “directly on,”“directly connected to” or “directly coupled to” another element orlayer, there are no intervening elements or layers present. Likereference numerals refer to like elements throughout the figures. Asused herein, the term “and/or” includes any and all combinations of oneor more of the associated listed items.

It will be understood that, although the terms first, second, third etc.may be used herein to describe various elements, components, regions,layers and/or sections, these elements, regions, layers and/or sectionsshould not be limited by these terms. These terms are only used todistinguish one element, region, layer or section from another element,region, layer or section. Thus, a first element, region, layer orsection discussed below could be termed a second element, region, layeror section without departing from the teachings of the presentinvention.

Spatially relative terms, such as “beneath,” “below,” “lower,” “above,”“upper”, “vertical”, and the like, may be used herein for ease ofdescription to describe one element or feature's relationship to anotherelement(s) or feature(s) as illustrated in the figures. It will beunderstood that the spatially relative terms are intended to encompassdifferent orientations of the device in use or operation in addition tothe orientation depicted in the figures. For example, if the device inthe figures is turned over, elements described as “below” or “beneath”other elements or features would then be oriented “above” the otherelements or features. Thus, the exemplary term “below” can encompassboth an orientation of above and below. The device may be otherwiseoriented (rotated 90 degrees or at other orientations) and the spatiallyrelative descriptors used herein interpreted accordingly.

FIG. 1 is a block diagram of a computer system including a computer 20hosting a removable memory card 10 including a flash memory deviceaccording to an embodiment of the present invention. The memory card 10further includes a flash memory controller (not shown) which controlsdata flow and commands between a memory interface I/F 25 in the hostcomputer 20 and the flash memory cells (not shown) in the memory card10. Examples of the computer 20 include personal computers, fileservers, peripheral devices, wireless devices, digital cameras, personaldigital assistants (PDA's), MP3 audio players, MPEG video players, andaudio recorders. The removable memory card will typically have a housingthat has a predetermined form factor and interface, such as SD (SecureDigital), MS (memory stick), CF (compact flash), SMC (smart media), MMC(multi media), or XD (XD-Picture Card), PCMCIA, CardBus, IDE, EIDE,SATA, SCSI, universal serial bus e.g., a USB flash drive) etc.

It will be appreciated by those skilled in the art that additionalcircuitry and control signals can be provided, and that the computersystem of FIG. 1 has been simplified.

FIG. 2 f is a side cross-sectional view of three portions of anintegrated circuit containing a memory device according to an embodimentof the present invention. FIG. 2 f shows the structure of transistors inthe memory device, formed in an integrated circuit on a substrate 101,according to an exemplary embodiment of the invention. In someembodiments of the present invention, the substrate 101 may include anintrinsic semiconductor (e.g., single crystal silicon, germanium,silicon-germanium, etc.) substrate, a silicon-on-insulator (SOI)substrate, a substrate having a thin film obtained by a selectiveepitaxial growth (SEG) process, etc. The memory device of FIG. 2 fincludes an array of non-volatile memory cells 131, and peripheralcircuitry including address circuitry, control circuitry, andInput/Output (I/O) circuitry formed of low voltage transistors (LVTs)136 and/or high voltage transistors (HVTs) 138. The memory cells 131 arealso referred to as flash memory cells wherein blocks of memory cellscan be erased concurrently in a flash operation.

Referring to FIG. 2 f, in a first (memory cell) portion (portion “a” onthe left side of FIG. 2 f) of the integrated circuit, the memory devicecontains a plurality of memory cells 131 connected in series (NAND-flashconfiguration) formed on a substrate 101 (101 a). The first transistor130 and last transistor 132 in each string may be a string selectiontransistor (SST) (also known as a Bit Line Select Transistor) and theGround Select Transistor (GST) respectively, while the middletransistors 134 constitute data storage cells.

In a second portion (middle of FIG. 2 f) of the integrated circuit, aplurality of low voltage transistors (LVT) 136 of the memory device areformed in a peripheral area of the integrated circuit formed on thesubstrate 101 b. In a third portion (right side of FIG. 20 of theintegrated circuit, the memory device contains a plurality of highvoltage transistors (LVT) 138 formed on the substrate 101. Thus, theflash memory device in FIG. 2 f may have three types of transistorswhich are composed of memory cells 131, low voltage transistors (LVT)136 and high voltage transistors (HVT) 138. The low voltage transistors(LVT) 136 and high voltage transistors (HVT) 138 may comprise theperipheral circuitry of the memory device. The corresponding tunnelbarrier layer portions 105 a, 105 b and 105 c in the three types oftransistors 131, LVT 136 and HVT 138 may be formed approximatelysimultaneously using the same process steps without patterning.

Referring to FIG. 2 f, a memory device includes a substrate 101 (101A,101B, and 101C) and a patterned transistor gate electrode layer (115and/or 119). Although only some patterned gate electrode structures(forming memory cells 131, LVT 136 and HVT 136) are depicted in FIG. 2f, it will be appreciated that the integrated circuit including thememory device may include a large number of patterned gates comprisingmemory cells and peripheral circuitry.

In the memory cells 131, between the substrate 101 a and the patternedgate electrode layer 119 is a tunneling insulating layer 105 a having afirst dielectric constant, a charge storage layer 107, and a blockinginsulating layer 117 having a second dielectric constant that may begreater than the first dielectric constant. The blocking insulatinglayer 117 may be formed of material selected from one of O/N/O,O/high-k/O, SiO₂, SiN, SiON, HfO₂, ZrO₂, Al₂O₃ or any combinationthereof.

The tunneling insulating layer (tunnel barrier layer) 105 a, the chargestorage layer 107, the blocking insulating layer 117, and the gateelectrode (comprised of first conductive layer 115 and/or a secondconductive layer 119) are sequentially stacked over an active (channel)region of a doped (e.g., P-type) semiconductor substrate 101. As shown,two N+ type impurity diffusions 128 are formed on opposite sides oftransistor channels and bound the active regions within memory cellportion “a” of the substrate 101.

In this exemplary embodiment, the tunnel barrier (105 a) within a memorycell 131 formed in portion “a” of the substrate 101 may have threelayers (e.g., 105-1, 105-2, 105-3). The first layer 105-1 is an oxidelayer that may be formed by an oxidation process (e.g., by thermaloxidation), or by chemical vapor deposition (CVD). The second layer105-2 may comprise SiON, SiN or other high-k material, e.g., Al₂O₃,HfO₂, HfSiON, ZrO₂, or a mixture thereof and may be formed by an atomiclayer deposition (ALD) deposition process or by chemical vapordeposition (CVD).

According to other embodiments of the present invention, the secondlayer 105-2 of the tunnel barrier may comprise metallic oxide ormetallic oxynitride of a group III element or group VB element in theMendeleev Periodic Table. According to other embodiments, the secondlayer 105-2 of the tunnel barrier may comprise doped metal oxide ordoped metal oxynitride in which metal oxide is doped with a group IVelement in the Mendeleev Periodic Table. The group IV element may bedoped with a metal oxide of about 0.1-30 weight percent. The secondlayer 105-2 of the tunnel barrier may also comprise one of La₂O₃,Hf_(1-x)Al_(x)O_(y), Hf_(x)Si_(1-x)O₂, Zr_(x)Si_(1-x)O₂,Zr—Si-oxynitride, or any combination thereof.

The third layer 105-3 of the tunnel barrier 105 is an oxide layer thatmay be formed by an anneal process, or by chemical vapor deposition(CVD). In various other exemplary embodiments, the tunnel barrier (105a) in the memory cells 131 may consist essentially of two layers (e.g.,105-1, 105-2) including the second (“nitride”) layer 105-2. In otherexemplary embodiments, the tunnel barrier (105 a) in the memory cells131 may consist essentially of one layer including the second(“nitride”) layer 105-2.

In the present exemplary embodiment shown in FIG. 2 f, the tunnelbarrier layer 105 a, 105 b, 105 c is formed after the completion of atleast one shallow trench isolation (STI) process has formed a pluralityof STIs 113 throughout the various portions of the substrate 101 (101A,101B, 101C). Thus, the tunnel barrier layer 105 (105 a, 105 b, 105 c) isformed over the oxide-filled STI trenches formed in each portion “a”,“b”, and “c” of the substrate 101 (101A, 101B, 101C). The STItrench-fill material may be formed of the same oxide composition as thematerial of the first (oxide) layer 105-1 of the tunnel barrier layer105 a, 105 b, 105 c. Thus, in effect, over the oxide-filled STI trenchesin at least portion “a”, “b”, of the substrate 101 (101A, 101B), thereare two layers which comprise the second (105-2) and the third (105-3)layers of the tunnel barrier layer 105 a, 105 b, 105 c. In someembodiments, the tunnel barrier layer 105 (105 a, 105 b, 105 c) formedwithin all of the three portions “a”, “b” and “c” of the integratedcircuit may be formed in one series of process steps that does notinclude patterning of one or more of the component layers 105-1, 105-2,105-3.

In the exemplary embodiment shown in FIG. 2 f, the tunnel barrier layer105 (105 b) comprised of three layers (105-1, 105-2, 105-3) is the gatedielectric between the gate electrode 115/119 of the low-voltagetransistor (LVT) and its channel in the semiconductor substrate 101 b.

A thicker gate dielectric (oxide dielectric layer 103) is typicallyrequired between the gate electrode 115/119 of the high-voltagetransistor (HVT) and its channel in the semiconductor substrate 101 c.Thus, the tunnel barrier layer 105 c in the high voltage transistor(HVT) in the peripheral portion “c” of the integrated circuit in effectcomprises the second (105-2) and the third (105-3) layers formed over athick first oxide layer 103 c (thicker 105-1).

The charge storage layer 107 may include nitrided silicon (e.g., Si₃N₄or silicon oxynitride SiON) silicon-rich oxide or ferroelectricmaterial. Charge trap technology is described in U.S. Pat. Nos.6,858,906, 7,253,467, and Application No. 20060180851, the disclosuresof which are collectively incorporated by reference herein in theirentirety.

A layer of photoresist material 121 (121 a, 121 b, 121 c) is patternedover the conductive layer(s) 115 and/or 119 and then the conductivelayer(s) 115 and/or 119 are etched and thereby patterned to form thegate electrodes of the individual transistors 130, 134, 132, 136, 138.The memory device according to this embodiment may further include aspacer 126 formed on the vertical sides of the patterned gate electrodesof the transistors. The spacer 126 and the patterned photoresistmaterial 121 may be used to pattern the charge storage layer 107 and theblocking insulating layer 117 formed over tunnel barrier layer 105 a.The spacer 126 and the patterned gate electrodes 115/119 may be used topattern the doping of the diffusion regions 128 in the substrate 101(101A, 101B, 101C).

FIGS. 2 a through 2 e are cross-sectional views depicting the steps of amethod of fabricating the memory device of FIG. 2 f.

Referring to FIG. 2 a, a thick gate dielectric (oxide) layer 103 isformed on the top of the substrate 101C for the gate dielectric ofhigh-voltage transistors (HVT) in the “c” portion of the integratedcircuit.

Referring to FIG. 2 b, a patterned mask layer (not shown) is formed onthe substrate 101 and on the HVT gate dielectric oxide 103. Using thepatterned mask, portions of the substrate 101 (101A, 101B, 101C) and ofthe HVT gate dielectric oxide 103 are removed to form trenches in thesubstrate 101. A trench filling material (e.g., silicon oxide) is formedon the resultant structure to fill the trenches. The trench filling ispartially removed by a chemical mechanical polishing (CMP) to expose themask layer, thereby forming active semiconductor regions (between STItrenches 113). Subsequently, a top portion of the STI fill is recessed,i.e., partially removed along with the patterned mask so that the topsurface of the STI is at the height of the top surface of the HVT gatedielectric oxide 103.

Referring to FIG. 2 c, the tunnel barrier layer 105 (105 a, 105 b, 105c) is formed without patterning upon all of the three portions “a”, “b”and “c” of the integrated circuit.

Referring to FIG. 2 d, the first conductive layer 115 (e.g., apolysilicon gate layer) is formed upon portions “b” and “c” of theintegrated circuit. The charge storage layer 107 is formed upon thetunnel barrier layer 105 within memory cell portion “a” of theintegrated circuit. The blocking insulating layer 117 is formed upon thecharge storage layer 107 within memory cell portion “a” of theintegrated circuit. The blocking insulating layer 117 can for example bedeposited by a technique such as atomic layer chemical vapor deposition(ALCVD).

Referring to FIG. 2 e, the second conductive layer 119 is formed uponthe blocking insulating layer 117 within memory cell portion “a” anddirectly upon the first conductive layer 115 within the LVT and HVTportions “b” and “c” of the integrated circuit. Then a patternedphotoresist layer 121 is formed as a gate mask upon the secondconductive layer 119. Then the regions of the first conductive layer 119and second conductive layer 115 not covered (overlapped) by thepatterned photo resist layer 121 are etched away to form the individualgate electrodes of the transistors 130, 132, 134, 136, and 138. Then thevertical sides of patterned gate electrodes of individual transistors130, 132, 134, 136, and 138 are covered with spacer (e.g., oxide) 126(see FIG. 2 f). The portions of the charge storage layer 107 and theblocking insulating layer 117 not covered (overlapped) by the spacer(e.g., oxide) 126 or the patterned photoresist layer 121 are removed.And then N+ type impurity diffusions 128 are formed on opposite sides oftransistor channels within the substrate 101. Thus transistors of thestorage cells 134 of the memory cell 131, the low-voltage transistors(LVT) 136 and the high-voltage transistors (HVT) 138 are completed.

As a result, the tunnel barrier layer 105, the first charge storagelayer 107, the blocking insulating layer 117, the gate electrode layer115/119 and the patterned photoresist layer 121 are formed on activeregions in all of portions “a”, “b” and “c” of the integrated circuit.And the tunnel barrier layer 105 (105 a, 105 b, 105 c) covers (overlaps)the STI fill in each of portions “a”, “b” and “c” of the integratedcircuit.

FIG. 3 f is a side cross-sectional view (e.g., parallel with a bit linenot shown) of three portions of an integrated circuit containing amemory device according to another embodiment of the present invention.FIG. 3 f shows the structure of transistors in the memory device, formedin an integrated circuit on a substrate 101, according to anotherexemplary embodiment of the invention. The memory device of FIG. 3 f issimilar to the memory device of FIG. 2 f except that the structure oflow-voltage transistors LVT and of high-voltage transistors HVT in thememory device of FIG. 3 f is different from those in the memory deviceof FIG. 2 f. The structure of transistors in the memory cells 131(transistors 130, 124, 132) in the memory device of FIG. 3 f are thesame as in the memory device of FIG. 2 f and a redundant descriptionthereof will be omitted.

Referring to FIG. 3 f, in the second portion (portion “b” in middle ofFIG. 3 f) of the integrated circuit, the plurality of low voltagetransistors (LVT) 136 of the memory device formed in the peripheral areaof the integrated circuit include gate dielectric 103 b, which can bemade essentially of oxide. In the third portion (portion “c” on rightside of FIG. 3 f) of the integrated circuit, the plurality of highvoltage transistors (LVT) 138 have gate dielectrics 103 c which can alsobe made essentially of oxide. As shown in FIG. 3 f, the respective gatedielectrics 103 b and 103 c of the low voltage transistors (LVT) 136 andof high voltage transistors (LVT) 138 do not contain the second(“nitride”) layer 105-2 of the tunnel barrier layer (105 a) that isformed over the substrate within the memory cell portion “a” of thememory device. The gate dielectric (oxide) 103 c of the high-voltagetransistor (HVT) 138 may be thicker than the gate dielectric (oxide) 103b of the low-voltage transistors (LVT) 136.

FIGS. 3 a through 3 e are side cross-sectional views depicting the stepsof a method of fabricating the memory device of FIG. 3 f.

Referring to FIG. 3 a, a dielectric (oxide) layer 103 is formed on thetop of the high-voltage transistor (HVT) portion “c” of the substrate101 for the gate dielectric of high-voltage transistors (HVT) in the “c”portion of the integrated circuit.

Referring to FIG. 3 b, a second dielectric (oxide) layer is formed onthe top of the portions “b” and “c” of the substrate 101 to form thegate dielectric oxide layer 103 b of the low voltage transistors (LVT)and the thicker gate dielectric oxide layer 103 c of the high-voltagetransistors (HVT) in the “b” and “c” portions of the integrated circuit.Then, a patterned mask layer (not shown) is formed on the substrate 101and on the LVT gate dielectric oxide 103 b and on the HVT gatedielectric oxide 103 c. Using the patterned mask, portions of thesubstrate 101 and of the LVT and HVT gate dielectric oxides 103 a and103 b are removed to form trenches in the substrate 101. A trenchfilling material (e.g., silicon oxide) is formed on the resultantstructure to fill the trenches. The trench filling is partially removedby a chemical mechanical polishing (CMP) to expose the mask layer,thereby forming active semiconductor regions (between STI trenches 113).Subsequently, a top portion of the STI fill is recessed, i.e., partiallyremoved along with the patterned mask so that the top surface of the STIis at the height of the top surface of the gate dielectric oxides 103 band 103 c.

Referring to FIG. 3 c, the first conductive layer 115 (e.g., apolysilicon gate layer) is formed upon portions “b” and “c” of theintegrated circuit, overlapping the STIs 113.

Referring to FIG. 3 d, the tunnel barrier layer 105 a, the chargestorage layer 107 and the blocking insulating layer 117 are sequentiallyformed upon the memory cell portion “a” of the substrate, overlappingthe STIs 113.

Referring to FIG. 3 e, the second conductive layer 119 (e.g., apolysilicon gate layer) is formed upon all of portions “a”, “b” and “c”of the integrated circuit. The second conductive layer 119 may be formeddirectly upon the first conductive layer 115 within the LVT and HVTportions “b” and “c” of the integrated circuit. Then a patterned photoresist layer 121 is formed as a gate mask upon the second conductivelayer 119.

Referring to FIG. 3 f, the regions of the first conductive layer 119 andsecond conductive layer 115 not covered (overlapped) by the patternedphoto resist layer 121 are etched away to form the individual gateelectrodes of the transistors 130, 132, 134, 136, and 138. Then thevertical sides of patterned gate electrodes of individual transistors130, 132, 134, 136, and 138 are covered with spacer (e.g., oxide) 126.The portions of the charge storage layer 107 and the blocking insulatinglayer 117 not covered (overlapped) by the spacer (e.g., oxide) 126 orthe patterned photoresist layer 121 are removed. And then N+ typeimpurity diffusions 128 are formed on opposite sides of transistorchannels within the substrate 101. Thus transistors of the storage cells134 of the memory cell 131, the low-voltage transistors (LVT) 136 andthe high-voltage transistors (HVT) 138 are formed.

As a result, the tunnel barrier layer 105, the first charge storagelayer 107, the blocking insulating layer 117, the gate electrode layer115/119 and the patterned photoresist layer 121 are formed on activeregions in all of portions “a”, “b” and “c” of the integrated circuit.And the tunnel barrier layer 105 (105 a) covers (overlaps) the STI inmemory cell portions “a”, but not portions “b” and “c”, of theintegrated circuit. However, the first charge storage layer 107, theblocking insulating layer 117 do not overlap any STI in the integratedcircuit.

FIG. 4 is a cross-sectional view (e.g., parallel with a bit line) (notshown) of three portions of an integrated circuit containing a memorydevice according to another embodiment of the present invention. FIG. 4shows the structure of transistors in the memory device, formed in anintegrated circuit on a substrate 101, according to another exemplaryembodiment of the invention.

The memory device of FIG. 4 is similar to the memory device of FIG. 2 fexcept that the layers of the transistors formed after the tunnelbarrier layer 105 (105 a, 105 b, 105 c) are patterned differently andthe doping of the N+ type impurity diffusions in the substrate (101 b,101 c) are patterned differently. These differences are due to the useof two spacers, inner spacer 126 and outer spacer 127, as patterneddoping masks.

Referring to FIG. 4, the corresponding tunnel barrier layer portions 105a, 105 b and 105 c in the three types of transistors 131, LVT 136 andHVT 138 may be formed approximately simultaneously using the sameprocess steps without patterning any of the component layers 105-1,105-2 and 105-3. Afterwards, a charge storage layer 107, and a blockinginsulating layer 117 are sequentially formed within the memory cell 131portion “a” of the integrated circuit. Afterwards conductive layer(s)115 and/or 119 are formed. Afterwards, a layer of photoresist material121 (121 a, 121 b, 121 c) is patterned over the conductive layer(s) 115and/or 119. Then the conductive layer(s) 115 and/or 119 are etched andthereby patterned to form the gate electrodes of individual transistors131, 136, 138 in all portions “a”, “b” and “c” of the integratedcircuit. Afterwards, an inner spacer is formed upon the vertical sidesof the patterned gate electrodes of individual transistors in all ofportions “a”, “b” and “c” of the integrated circuit. Afterwards, theinner spacer 126 is used as a mask, to cut (pattern) the blockinginsulating layer 117 and charge trap layer 107 (forming individualcharge storage regions) within the memory cell 131 portion “a” of theintegrated circuit. Afterwards, an outer spacer 127 is formed upon theapproximately vertical sides of the inner spacer 126 in all of portions“a”, “b” and “c” of the integrated circuit. Afterwards, the outer spacer127 is used as a mask, to pattern the doping of the N+ type impuritydiffusions 128 in the substrate (101 a, 101 b, 101 c) in all of portions“a”, “b” and “c” of the integrated circuit. The N+ type impuritydiffusions 128 may be formed by ion implantation and/or other diffusionmethods. In alternative embodiments, the memory devices shown in FIG. 3f may be similarly modified similarly using two spacers (126 and 127) aspattern masks, instead of using only one such spacer 126, to cut(pattern) the blocking insulating layer 117 and charge trap layer 107(forming individual charge storage regions).

FIG. 5 h is a side cross-sectional view of three portions of anintegrated circuit containing a memory device according to anotherembodiment of the present invention. FIG. 5 h shows the structure oftransistors in the memory device, formed in an integrated circuit on asubstrate 101, according to another exemplary embodiment of theinvention.

The memory device of FIG. 5 h differs from the memory device of FIG. 2 fin that that some of the layers formed above the tunnel barrier layer105 (105 a, 105 b, 105 c) are different. This difference is due to theuse of a first conductive layer 115 as a charge storage layer (floatinggate) of storage cells 134, and the use of butting contacts 119 abetween the first conductive layer 115 and the second conductive layer119 to form gate electrodes of the other individual transistors 130,132, 136, 138. The floating gate 115 may consist of highly N-type dopedpolysilicon. The information that is stored in the memory cell isdetermined by the charge on the floating gate 115. The readout of thestorage cells 134 can be done by using the gate electrodes 119.

In the present exemplary embodiment shown in FIG. 5 h, the tunnelbarrier layer 105 (105 a, 105 b, 105 c) is formed before shallow trenchisolation (STI) process has formed a plurality of STIs 113 throughoutthe various portions of the substrate 101 (101A, 101B, 101C). The tunnelbarrier layer 105 (105 a, 105 b, 105 c) including the second (“nitride”)layer 105-2 is cut by the oxide-filled STI trenches formed in eachportion “a”, “b”, and “c” of the substrate 101 (101A, 101B, 101C). Thetunnel barrier layer 105 (105 a, 105 b, 105 c) including the second(“nitride”) layer 105-2 is included in the gate dielectric of each ofindividual transistors 130, 132, 136, and 138. In the exemplaryembodiment shown in FIG. 5 h, the tunnel barrier layer 105 (105 b)comprised of three layers (105-1, 105-2, 105-3) is the gate dielectricbetween the gate electrode 115/119 of the low-voltage transistor (LVT)and its channel in the semiconductor substrate 101 b. Thus tunnelbarrier layer 105 (105 a, 105 b, 105 c) including the second (“nitride”)layer 105-2 is the entire gate dielectric of each of individualtransistors 130, 132, and 136.

In some embodiments, the tunnel barrier layer 105 (105 a, 105 b, 105 c)formed within all of the three portions “a”, “b” and “c” of theintegrated circuit may be formed in one series of process steps thatdoes not include patterning (other than by formation of the STI trenches113) of one or more of the component layers 105-1, 105-2, 105-3.

FIGS. 5 a through 5 g are cross-sectional views depicting the steps of amethod of fabricating the memory device of FIG. 5 h.

Referring to FIG. 5 a, a thick gate dielectric (oxide) layer 103 isformed on the top of the substrate 101C for part of the gate dielectrichigh-voltage transistors (HVT) in the “c” portion of the integratedcircuit.

Referring to FIG. 5 b, the tunnel barrier layer 105 (105 a, 105 b, 105c) is formed without patterning upon all of the three portions “a”, “b”and “c” of the integrated circuit, directly upon the substrate 100 (101Aand 101B) and directly upon the thick gate dielectric (oxide) layer 103.

Referring to FIG. 5 c, a buffer layer 109 is formed without patterningupon all of the three portions “a”, “b” and “c” of the integratedcircuit, directly upon the tunnel barrier layer 105 (105 a, 105 b, 105c). Then, a stopper layer 111 is formed without patterning upon all ofthe three portions “a”, “b” and “c” of the integrated circuit, directlyupon the buffer layer 109. Then a patterned mask layer (not shown) isformed upon the stopper layer 111. Using the patterned mask, portions ofthe stopper layer 111, of the buffer layer 109, of the tunnel barrierlayer 105 (105 a, 105 b, 105 c), of the HVT gate dielectric oxide 103,and of the substrate 101 and are removed to form trenches in thesubstrate 101 (101A, 101B, 101C). A trench filling material (e.g.,silicon oxide) is formed on the resultant structure to fill thetrenches. The trench filling is partially removed (e.g., by a chemicalmechanical polishing (CMP)) to expose the stopper layer 111 and/or thebuffer layer 109.

Referring to FIG. 5 d, the stopper layer 111 and the buffer layer 109are removed (e.g., by chemical etching) down to the top surface of thetunnel barrier layer 105, leaving recesses between and lower than thetop surface of the STIs in the substrate 101 (101A, 101B, 101C).

Referring to FIG. 5 e, the first conductive layer 115 (e.g., apolysilicon gate layer) is formed without patterning upon the tunnelbarrier layer 105 (105 a, 105 b, 105 c) in all of portions “b” and “c”of the integrated circuit, also filling in the recesses between andcovering the top surface of the STIs. Within the memory cell 131 portion“a” of the memory device, the first conductive layer 115 (subsequentlypatterned) will constitute a charge storage layer (floating gate) formedupon the tunnel barrier layer 105.

Referring to FIG. 5 f, the blocking insulating layer 117 is formed andpatterned upon the first conductive layer 115 within all of portions“a”, “b” and “c” of the memory device. The patterning of the blockinginsulating layer 117 creates a plurality of through-holes 118 a down tothe top surface of the first conductive layer 115, for subsequentfilling with a conductive material 119 to form a plurality of buttingcontacts (119 a, see FIG. 5 g).

Referring to FIG. 5 g, the second conductive layer 119 is formed withoutpatterning upon the patterned blocking insulating layer 117, filling theplurality of through-holes 118 a down to the top surface of the firstconductive layer 115 (forming a plurality of butting contacts 119 a),within all portions “a”, “b”, and “c” of the memory device. Then apatterned photo resist layer 121 (121 a, 121 b, 121 c) is formed as agate mask upon the second conductive layer 119. Then the regions of thefirst conductive layer 119, of the blocking insulating layer 117, and ofsecond conductive layer 115 not covered (overlapped) by the patternedphoto resist layer 121 (121 a, 121 b, 121 c) are etched away to form theindividual gate electrodes of the transistors 130, 132, 134, 136, and138. Floating gates are also formed from the first conductive layer 115in storage cells 134.

Referring again to FIG. 5 h, the vertical sides of patterned gateelectrodes of individual transistors 130, 132, 134, 136, and 138 arecovered with spacer (e.g., oxide) 126. And then N+ type impuritydiffusions 128 are formed on opposite sides of transistor channelswithin the substrate 101. Thus transistors of the memory cell 131, thelow-voltage transistors (LVT) 136 and the high-voltage transistors (HVT)138 are completed.

As a result, the tunnel barrier layer 105, are formed upon activeregions in all of portions “a”, “b” and “c” of the integrated circuit.The tunnel barrier layer 105 (105 a, 105 b, 105 c) does not cover(overlap) the STIs in any of portions “a”, “b” and “c” of the integratedcircuit. The tunnel barrier layer 105 constitutes the entire gatedielectric of the transistors 130 and 132 in the memory cells 131 and ofthe low-voltage transistors (LVT). The tunnel barrier layer 105 (105C)constitutes part of the gate dielectric (105 c+103) in the high-voltagetransistors (HVT).

FIG. 6 is a block diagram of a computer system including a flash memorydrive according to an exemplary embodiment of the present invention.

FIG. 6 is a block diagram of a computer system 600 including a memorysystem 1310 including a flash memory device 1311 according to anembodiment of the present invention. The memory device 1311 is coupledto a memory controller 1312 for accessing the flash memory cell array inthe flash memory device 1311. The flash memory device 1311 coupled tothe memory controller 1312 forms part of the computer system 600. Someexamples of the computer system 600 include personal computers,peripheral devices, wireless devices, digital cameras, personal digitalassistants (PDA's), MP3 audio players, MPEG video players, digital audiorecorders, and digital video recorders. The memory system 1310 can be amemory card-based hard-drive, a Solid State Disk SSD (CIS), a hybrid(SSD/magnetic) disk, a Camera Image Processor (CIS) or a memory coreintegrated with the CPU 1330.

The memory device 1311 of the memory system 1310 of FIG. 6 receivescontrol signals across control lines from the system bus 1360 via thememory controller 1312 to control access to the memory cell array in thememory device 1311. Access to the memory cell array in the memory device1311 is directed to one or more target memory cells by integratedtransistors in peripheral circuitry and via word lines and bit lines inthe memory device 1311. Once the memory cell array is accessed inresponse to the control signals and the address signals, data is writtento or read from the memory cells by the integrated transistors in theperipheral circuitry in the memory device 1311.

The memory device 1310 of the memory system 1310 of FIG. 6, and thememory device in the memory card 1210 of FIG. 1 can be mounted invarious package types, including Ball Grid Arrays (BGAs), Chip ScalePackages (CSPs), Plastic Leaded Chip Carrier (PLCC), Plastic DualIn-Line Package (PDIP), Multi Chip Package (MCP), Wafer-level FabricatedPackage (WFP), Wafer-Level Processed Stack Package (WSP).

As described above, in memory devices in accordance with exemplaryembodiments of the invention, memory cells, the low voltage transistors,and high voltage transistors operating at a relatively higher voltageare integrated and formed using the same process steps, thus increasingmanufacturing efficiency.

Having thus described exemplary embodiments of the present invention, itis to be understood that the invention defined by the appended claims isnot to be limited by particular details set forth in the abovedescription as many apparent variations thereof are possible withoutdeparting from the spirit or scope thereof as hereinafter claimed.

1. A method of forming an integrated circuit on a substrate, theintegrated circuit having a memory cell region including a plurality ofmemory cell transistors each having a gate electrode, and a peripheralregion including low voltage transistors (LVT) and high voltagetransistors (HVT) outside of the memory cell region, the methodcomprising: forming a first trench isolation (TI) within the memory cellregion for isolating at least one of the memory cell transistors, andforming a second trench isolation (TI) for isolating at least one of thelow voltage transistors (LVT) and forming a third trench isolation (TI)for isolating at least one of the high voltage transistors (HVT); andforming a tunnel barrier layer having first and second dielectric layerswithin the memory cell region between the gate electrodes of the memorycell transistors and the substrate, and within the peripheral region. 2.The method of claim 1, wherein forming the tunnel barrier layer withinthe peripheral region includes forming the tunnel barrier layer withinthe low voltage transistors (LVT) and within the high voltagetransistors (HVT).
 3. The method of claim 1, wherein the step of formingthe tunnel barrier layer comprises the substeps of: forming the firstdielectric layer; forming the second dielectric layer upon the firstdielectric layer; and forming a third dielectric layer upon the a seconddielectric layer, wherein the first dielectric layer is an oxide layer,the second dielectric layer is a nitride layer, and the third dielectriclayer is an oxide layer.
 4. The method of claim 1, wherein the first,second, and third trench isolation are formed prior to forming thetunnel barrier layer, and the tunnel barrier layer is formed upon thefirst trench isolation.
 5. The method of claim 1, wherein the firsttrench isolation, the second trench isolation, and the third trenchisolation are formed prior to forming the tunnel barrier layer, and thetunnel barrier layer is formed upon the second trench isolation and uponthe third trench isolation.
 6. The method of claim 1, wherein the firsttrench isolation, the second trench isolation, and the third trenchisolation are formed after forming the tunnel barrier layer, and thetunnel barrier layer is not formed upon the first trench isolation, norupon the second trench isolation nor upon the third trench isolation. 7.The method of claim 1, wherein the step of forming the first trenchisolation, the second trench isolation and the third trench isolationincludes the substeps of: forming a buffer layer (109) upon the tunnelbarrier layer; forming a stopper layer upon the buffer layer; etchingthe buffer layer, the stopper layer, and the substrate to form thetrenches; filling the trenches; and removing the buffer layer andstopper layer.
 8. The method of claim 1, further comprising the stepsof: forming a first conductive layer upon the tunnel barrier layer;forming a blocking insulating layer upon the first conductive layer;patterning the blocking insulating layer within the peripheral region toform butting contact holes; patterning the blocking insulating layerwithin the memory cell region to form gate dielectrics of the memorycell transistors and butting contacts holes; forming a second conductivelayer upon the patterned blocking insulating layer and forming buttingcontacts connecting the first conductive layer and the second conductivelayer within the gate electrodes of the LVT and HVT in the peripheralregion; and patterning the second conductive layer, the blockinginsulating layer, and the first conductive layer within the peripheralregion.
 9. A method of forming an integrated circuit on a substrate, theintegrated circuit having a memory cell region including a plurality ofmemory cell transistors each having a gate electrode, and a peripheralregion including low voltage transistors (LVT) and high voltagetransistors (HVT), outside of the memory cell region, the methodcomprising: forming the gate oxide layer upon the substrate within theperipheral region; forming a first trench isolation (TI) within thememory cell region for isolating at least one of the memory celltransistors, and forming a second trench isolation (TI) for isolating atleast one of the low voltage transistors (LVT) and forming a thirdtrench isolation (TI) for isolating at least one of the high voltagetransistors (HVT); and forming a tunnel barrier layer having first andsecond dielectric layers within the memory cell region between the gateelectrodes of the memory cell transistors and the substrate, and uponthe first trench isolation (TI) in the memory cell region, wherein thegate oxide layer is thicker than the tunnel barrier layer.
 10. Themethod of claim 9, wherein the step of forming the tunnel barrier layercomprises the substeps of: forming the first dielectric layer; formingthe second dielectric layer upon the first dielectric layer; and forminga third dielectric layer upon the a second dielectric layer, wherein thefirst dielectric layer is an oxide layer, the second dielectric layer isa nitride layer, and the third dielectric layer is an oxide layer. 11.The method of claim 9, further comprising the steps of: forming a chargestorage layer of the memory cell transistors upon the tunnel barrierlayer of the within the memory cell region; forming blocking insulatinglayer of the memory cell transistors within the memory cell region,wherein the blocking insulating layer comprises a selection from thegroup consisting of SiO2, SiN, SiON, HfO2, ZrO, and Al2O3; forming agate electrode conductive layer upon the blocking insulating layer ofthe memory cell transistors within the memory cell region; andpatterning the blocking insulating layer, the charge storage layer andthe gate electrode conductive layer of the memory cell transistorswithin the memory cell region.
 12. The method of claim 9, furthercomprising the steps of: patterning the blocking insulating layer, thecharge storage layer and the gate electrode conductive layer of thememory cell transistors within the memory cell region; forming innerspacers upon the vertical sides of the patterned blocking insulatinglayer, the charge storage layer and the gate electrode conductive layerof the memory cell transistors within the memory cell region; patterningthe blocking insulating layer and the charge storage layer using theinner spacers as a mask; forming outer spacers upon the inner spacers;and doping the substrate using the outer spacers as a mask.